Most of the commercially available vaccine preparations are in the form of injections. Injectable vaccines induce immune responses in the blood, i.e. systemic immune responses (production of IgG antibodies), but induce no mucosal immune responses (production of IgA antibodies). Although they can prevent the proliferation of pathogens after infection, such vaccines have difficulty in preventing the infection itself of pathogens via the mucosal routes.
This difficulty currently arouses an attention to mucosal vaccination, and vaccine researchers especially direct their attention to the development of vaccines for mucosal administration (nasal administration) using influenza viruses as antigens.
Vaccines for mucosal administration can induce not only systemic immunity (production of IgG antibodies) but also mucosal immunity (production of IgA antibodies). The IgA antibodies characteristically do not strictly distinguish the types of pathogens of the target disease. Thus, the IgA antibodies can respond to possible annual changes in types of circulating pathogens, and are considered to be effective in preventing pandemics.
One reason for such attention to vaccines for nasal administration is as follows. That is, administration of an antigen to a digestive tract mucosa is easily affected by gastric acid and proteases and is difficult to avoid such affection; in contrast, administration of an antigen via a nasal mucosa is not affected by such factors. Another reason is that the nasal mucosa has an antigen-recognizing tissue, called NALT, thereon and this tissue is effective for immune responses.
The following documents report examples of vaccines for nasal administration.
Patent Literature 1 proposes a Pantoea-derived lipopolysaccharide (LPS) and discloses that this LPS is safer and more enhances an immune response than conventional LPSs when administered together with an antigen.
However, Patent Literature 1 fails to mention or exemplify clearly the use of acquired immunity and to show an optimal ratio between the adjuvant and the antigen. Patent Literature 1 further fails to mention clearly the use of a Pantoea-derived LPS as a mucosal vaccine.
Patent Literature 2 proposes an inactivated antigen of a pathogen and, as an immunostimulant (adjuvant), a vaccine including a combination of Poly (I:C) and zymosan. The literature discloses one example using a lipopolysaccharide (LPS) derived from Pantoea agglomerans as an adjuvant and an influenza virus as a pathogen.
Still, the vaccine disclosed in Patent Literature 2 is unclear whether or not it can affect antigens other than the influenza viruses when nasally administered.